Usleep() function in C
In this article, we will discuss the usleep() function in C with its syntax, parameters, and examples.
The usleep() function in C programming is used to induce a delay or pause in a program's execution for a given amount of microseconds. It is commonly accessible on Unix-based systems, such as Linux and macOS, and is a part of the POSIX standard (Portable Operating System Interface for Unix).
Syntax of Usleep()'s function:
It has the following syntax:
int usleep(useconds_t microseconds);
Parameters:
microseconds: A type useconds_t unsigned integer expressing the number of microseconds to sleep.
Return Value: If successful, the usleep() method returns zero. In the event of an error, it returns -1 and sets the errno variable to the type of error.
Delay Duration: The amount of time that usleep() delays execution is provided in microseconds. One millionth (1/1,000,000) of a second is known as a microsecond (s).
Usage: The <unistd h> header file must be included to utilize the usleep() function. The program will wait for the specified number of microseconds after calling the function before proceeding.
The number of microseconds to sleep is represented by the unsigned integer microseconds, which is of type useconds_t in this case.
Remember that the operating system's scheduling of jobs makes it possible for the actual delay to be inaccurate, making the use of usleep() not advised for exact timing purposes. You should think about utilizing additional methods, such as the nanosleep() function or system-specific high-resolution clocks, for more accurate timing.
Since C11, the usleep() function has been regarded as deprecated. It is advised to use the nanosleep() function, which offers greater precision. You can define the delay in both seconds and nanoseconds using the POSIX-compliant nanosleep() method.
Here's an example of the usage of usleep():
Code:
#include <stdio.h>
#include <unistd.h>
int main()
{
int i;
for (i = 5; i>= 0; i--)
{
printf("Countdown: %d\n", i);
usleep(1000000);
// Sleep for 1 second (1000000 microseconds)
}
printf("Blastoff!\n");
return 0;
}
Output:
Countdown: 5
Countdown: 4
Countdown: 3
Countdown: 2
Countdown: 1
Countdown: 0
Blastoff!
Explanation:
In this example, the program will display a countdown, with a delay of one second between each count, from 5 to 0. The loop's execution is delayed by one-second due to the usleep(1000000) function call. The usleep() function will pause the running of the program for 1 second, or 1,000,000 microseconds.
It is important to keep in mind that the real delay might not be exactly one second due to the operating system schedules processes. However, this illustration provides you with a fundamental understanding of how to utilize usleep() to add a delay to your C programs.
Advantages and disadvantages of the usleep() function in C:
Advantages:
- Microsecond-Level Delay: It enables you to implement microsecond-level delays, which is useful in circumstances when accurate timing in microseconds is required, such as real-time applications and hardware interfaces.
- Convenience: The use of the usleep() function is simple. Only the quantity of microseconds you wish to pause for needs to be specified; the function takes care of the delay on your behalf.
- Cross-Platform Support: The usleep() function is a regularly used function on Unix-based systems and several non-POSIX platforms, even though it is not included in the C standard itself. Because of this, the code may be more platform-portable.
Disadvantages:
- Inaccuracy: Due to system scheduling and granularity restrictions, the actual delay generated by the usleep() function may not be exact. Use more sophisticated timer mechanisms or real-time extensions for highly precise timing requirements.
- Deprecation: The usleep() function is a deprecated function as of C11 and should not be used. It is advised to use the nanosleep() function as an alternative because it offers higher precision and lets you define the delay in both seconds and nanoseconds.
- Blocking Behaviour: During the time that the process is blocked by usleep(), it is sleeping. Usleep() function might not be the best option in situations involving multi-threaded programs or if you must carry out other operations concurrently.
- Non-Standard Function: Relying on usleep() may make your code less portable if you plan to run it on systems that do not support it because it is not a part of the C standard.
- Alternative Functions: Additional functions, such as nanosleep() and system-specific high-resolution clocks, provide greater accuracy and more reliable timing capabilities.
Conclusion:
In conclusion, the usleep() function has several advantages and disadvantages that you should take into account, even though it can be handy for simple temporal delays. Depending on your individual needs, it's advised to utilize additional timing functions such as nanosleep() or platform-specific timers for more accurate timing and better portability.